Generally a papermaking machine comprises a forming section, a press section and a dryer section. Papermakers fabrics transport an aqueous paper web through the machine to produce a paper product. Each of the three sections of the papermaking machine has its own unique characteristics and requirements. Accordingly, papermakers fabrics are specifically designed for each section of the papermaking machine such as forming fabrics for the forming section, wet press felts for the press section and dryer fabrics for the dryer section.
After a paper sheet is made by the conventional forming, pressing and drying operations, additional papermaking equipment can be used to manufacture corrugated material such as corrugated cardboard. As in the preliminary papermaking steps, a papermakers fabric is employed to transport the paper product during its manufacture. A corrugation machine combines separate paper sheets with an adhesive to form the corrugated paper product. As with other papermaking operations, the corrugation machine has its own unique demands on the performance of the papermakers fabric which transports the paper products therethrough.
Conventionally, corrugator belts, i.e. papermakers fabrics for corrugation machine, comprising a base fabric having one or more batts needled thereto have been utilized for the corrugation processing. Attempts have been made to utilize woven fabrics without batts as corrugation belts. For example, corrugator belts have been made having a woven fabric comprised entirely of spun polyester and polyester multifilament yarns in a three ply/three warp weave construction. Such fabrics are characterized by their relatively high weight, on the order of 20.59 oz./sq. ft., and low permeability, on the order of 4 CFM. (CFM as used herein means cubic feet per minute per square foot of fabric at 1/2 inch water pressure drop.)
At least one attempt has been made to provide a lightweight, high permeability fabric by constructing a 41/2 ply fabric with monofilament polyester warp yarns and a combination of monofilament polyester, spun polyester and spun acrylic filling yarn layers. Although such fabric was relatively lightweight, on the order of 9.38 oz./sq. ft., and had relatively high permeability, on the order of 19 CFM, the caliper of the fabric was only 0.161 inches and the fabric had a relatively high moisture absorption characteristic.
It is desirable to provide a papermakers fabric for corrugation papermaking equipment which is relatively lightweight and permeable and which has a sufficient caliper to provide the fabric thickness desirable for processing associated with corrugation.